Re: NANFA-L-- Diversity Indicies

Todd D. Crail (tcrail at UTNet.UToledo.Edu)
Fri, 30 Sep 2005 13:56:08 -0400

Thanks Dave. Yes it's been a tremendous help. Any time I get stuck, since
some of things I try to work with don't exactly have a book I can just refer
to... I like to post things out here because 1) it keeps me honest and 2) I
have to make defensible statements. The list is great for forming that
situation. For example, the whole sandbed thing. I don't think I would
have ever figured out it was the stupid thing "breathing" too much at night
if I hadn't posted it. It was a simple problem, had a simple solution, but
you can't solve it if you'd don't know what it is :)

Thanks also to Jan for his input. That is a bunch of valuable info. Now I
just need to sort through everything.... But for the first time ever, I lost
myself in the numbers this morning tinkering with how to present it, so I
guess that's a good thing :)

I also especially liked Martin's Dilbert character.

I was playing with the trophic guilds this morning. There may really be
something there. Instead of having "species tolerances" which is variable
and arguable, I would instead use "trophic guild tolerances", which I think
makes it clear what I'm really trying to say, and goes along with the fish
_community_ as THE response variable.

Species that are omnivorous like bluntnose and goldfish or tolerant
herbivores like stonerollers could have a value of 1, general insectivores
and insectivore/predators like striped shiner and grass pickerel a value of
2, and then your benthic insectivores such as darters and suckers a value of
3. Build an overall score and proportion from that and see what comes of
it. I think that corresponds well with habitat quality and who you would
find where. Heck even the water quality demanding species (sculpin, dace,
lamprey), perhaps they're all "4's" in the Maumee River watershed. Holey
moley, that would hold up. And it accounts for biomass, everything really

So if you knew in your system that you had that RARE stoneroller, you could
make an argument to assign it a "4" and go from there. Or maybe it's even a
"5". As long as you set your scale, limited your universe (say by
watershed), and remained consistent, scores in that watershed would be
comparable among other scores in that watershed. Right? Then you could run
your stats on the scores? Hmmm... Call it the "trophic guild score" or
something. Would it need a denominator? The insect trophic guild stuff
doesn't does it?

I dunno... Maybe just a simplification of the IBI, but that seems to be a
welcome proposition :) It would also help out when I get a seine load of
bluntnose and fathead where I sample 100 individuals but only 2 species with
50 of each species. If I get 20 darters at a site, that'll count 60 toward
the "site score", which most likely had 50 bluntnose as well.

The Muddy Maumee Madness, Toledo, OH
It's never too late to have a happy childhood.
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